1. Field of the Invention
The present invention relates generally to data transceivers.
2. Background Art
A communication device including a transmitter and a receiver is known as a transceiver. Known transceivers can transmit and receive data signals. There are demands on such transceivers to transmit and receive such data signals with low error rates and at ever increasing data rates, to reduce power dissipation, cost, and size. Therefore, there is a general need for a transceiver capable of satisfying such demands.
It is desirable to integrate transceiver circuits on an integrated circuit (IC) chip to reduce size and power dissipation of the transceiver. The circuits on the IC chip typically operate in accordance with timing signals. However, oscillators used to generate such timing signals have disadvantages, including typically large sizes, high power dissipation, and deleterious electromagnetic radiative properties (that is, the oscillators tend to radiate electromagnetic interference across the IC chip). Also, oscillators used in communication devices often need to be tunable in both phase and frequency and in response to rapidly changing signals. This requires complex oscillator circuitry. Moreover, multiple oscillators on a common IC chip are subjected to undesired phenomena, such as phase and/or frequency injection locking, whereby one oscillator can deleteriously influence the operation of another oscillator.
Therefore, there is a general need to integrate transceiver circuits on an IC chip. There is a related need to reduce the number and complexity of oscillators constructed on the IC chip, to thereby avoid or substantially reduce all of the above-mentioned disadvantages associated with such oscillators.
To reliably process a received data signal, a receiver typically needs to match its operating characteristics with the characteristics of the received data signal. For example, in the case of baseband data transmissions, the receiver can derive a sampling signal, and then use the sampling signal to sample the received data signal at sample times that produce optimal data recovery. In this way, data recovery errors can be minimized.
Precision timing control techniques are required to achieve and maintain such optimal sampling times, especially when the received data signals have high data rates, such as multi-gigabit-per-second data rates. Such timing control includes control of the phase and frequency of a sampling signal used to sample the received data signal.
As the received data signal rate increases into the multi-gigabit-per-second range, the difficulty in effectively controlling sampling processes in the receiver (such as controlling phase and frequency characteristics of the sampling signal) correspondingly increases. For example, semiconductor circuits, such as complementary metal oxide semiconductor (CMOS) circuits, are often unable to operate at sufficiently high frequencies to optimally control the sampling processes. For example, it becomes increasingly difficult at such high received signal data rates to provide sufficiently short time delays usable for controlling sampling phases of the sampling signal.
Accordingly, there is a need for systems and techniques in a data receiver that provide effective sampling of high data rate signals. There is a related need to reduce the number of circuit components required to provide such effective data signal sampling, thereby reducing cost, size, and power dissipation in the data receiver.